This invention is applicable generally to placing structural materials containing an inorganic alkaline sealant (for example, portland cement) to form a substantially rocklike mass useful for sealing and the like. Release of alkalinity from the mass also may be employed for protecting adjacent metal parts from corrosion. Although the invention clearly has much wide applicability, for ease of presentation it will be discussed here with reference to specific application in an underground pipeline and more particularly to joints in such an underground pipeline having metal parts which need to be protected from corrosion. In the usual practice of laying a pipeline for underground service, the pipes are placed in an open trench with a spigot end of one pipe fitted into a bell end of a last laid adjoining pipe. Such underground pipelines frequently are made of reinforced or prestressed concrete pipes each fitted with a steel bell ring at one of its ends and a steel spigot ring at its other end. Generally the spigot ring has an annularly formed groove into which is positioned a rubber gasket. When the spigot containing the gasket is inserted into the bell of the last laid pipe, the rubber gasket is compressed between the spigot groove and an inside annular face of the bell, thus effecting a watertight joint. Because of necessity of providing this means of joining and compressing the gasket, adjacent portions of the bell and spigot rings necessarily are exposed and may be subjected to corrosive influences depending upon character of enveloping soil and presence of moisture.
It has been customery practice to apply a diaper like form of burlap or the like (and generally referred to in industry as a "diaper") around the joint and to pour portland cement grout therein. When installed properly, the diaper offers an excellent means of assuring long term protection of the joint; however, both field and laboratory observations have shown that commonly there has been a lack of proper workmanship in installing such diapers, with the result that full value of these diapers often has not been realized. In part this lack is due to difficulty involved in proper application of the diapers and in part to inability of providing foolproof inspection of the diapered joints prior to their burial.
Another disadvantage of protecting the joints with mortar poured into diapers is excessive cost. A contractor is obliged to use at least one extra man performing the operation, even in the smallest of pipe sizes. For larger pipe sizes, a larger crew is needed together with necessary mixing and logistical support equipment. A further disadvantage is a requirement that excavated trenches which may fill with water generally percolating in from surrounding soil, must be dewatered prior to placement of the diapers and pouring of the grout. Yet another disadvantage of this method is a difficulty that grout pouring crews have in maintaining a proper sequence of trenching, pipe joining and backfilling. It is usual, therfore, to have excessively long lengths of open trenches with exposed joints being readied for grouting. Long lengths of open trenches pose hazards to the public and present an unsightly appearance. Cold weather is a further problem because pouring grout then requires apparatus to keep it at proper levels of temperature.